Self-cleaning oven

ABSTRACT

In apparatus for automatically heat-cleaning the interior surfaces of an oven having a locking member for locking the oven door during the cleaning process; a timer for controlling the cleaning operation; a blocking device for maintaining the door in its locked position during the operation; and a bimetal control device connected to the timer and the blocking device for actuating the blocking device and for preventing the timer from being reset after the cleaning operation has begun and while the temperature in the oven remains above a certain value.

United, States Patent 91 Pirker et ,al.

[451 Dec. 4, 1973 4] SELF-CLEANING OVEN [75] Inventors: Rudolf Pirker, Noremberg; Roland Kelchner, Furth/Bayem, both of Germany [73] Assignee: Licentia Patent-verwaltungs G.m.b.H., Frankfurt am Main, Germany 22 Filed: Nov. 9, 1972 [21] App]. No.: 304,951

[30] Foreign Application Priority Data Nov. 9, 1971 Germany P 21 55 570.4

[52] US. Cl. 126/197 [51] F24c 15/02 [58] Field of Search 126/197, 273, 19,

[56] References Cited UNITED STATES PATENTS 3,313,918 4/1967 Barber 126/197 X 3,416,515 12/1968 Mertler 126/197 X 3,469,568 9/1969 Torrey et a1. 3,638,638 2/1972 Phifer 126/197 Primary Examiner-Edward G. Favors Attorney-George 1-1. Spencer et a1.

[57] ABSTRACT In apparatus for automatically heat-cleaning the interior surfaces of an oven having a locking member for locking the oven door during the cleaning process; a timer for controlling the cleaning operation; a blocking device for maintaining the door in its locked position during the operation; and a bimetal control device connected to the timer and the blocking device for actuating the blocking device and for preventing the timer from being reset after the cleaning operation has begun and while the temperature in the oven remains above a certain value.

4 Claims, 5 Drawing Figures SHEET 2 CF 4 1 SELF-CLEANING OVEN BACKGROUND OF THE INVENTION The present inventionfrelates to kitchen ranges, particularly ranges provided with devices for automatically cleaning the interior surfaces of the oven, such as disclosed in US Pat. No. 3,625,197, issued to Priker et al; on Dec. 7, 1971.

The cleaning operation in such ranges is generally carried out by heating the oven to a relatively high temperature which is significantly above the normal operating temperature of the oven. It, therefore, is desirable, as a safety precaution, to maintain the oven door in a locked position during the cleaning process. A locking device is provided for locking the oven door during the cleaning operation and includes a locking element which is held under spring tension and which can be brought into its locking position relative to the oven door when the cleaning operation is initiated. Such apparatus is generally equipped with a timer which controls the cleaning operation and which works incooperation with the locking device. A blocking device is alsoprovided for holding the locking element in position during the cleaning operation.

In a kitchen range of this type the locking element is held in its locked position during the heat-cleaning process, after being inserted into the oven door, by means of a bimetal control device, so that the oven door cannot be opened. The timer switch used in this type of kitchen range is generally designed so that a friction coupling or similar device permits the winding knob, whichis disposed insidethe timer for winding the same to beturned in both directions. Such a bidirectional device is of particular advantage when the operation and manipulation of the timer on the kitchen range is being demonstrated. However, during the heat-cleaning process this device in the timer has the drawback that the time period set for a heat-cleaning process can be accidentally changed by turning forward the timer switch. This would result in a lengthening of the time period during which the oven is heated to the high cleaning temperature which could produce serious damage to the. equipment.

SUMMARY OF THE INVENTION An object of the present invention is to prevent any possible resetting of the timer during the cleaning period and thus an increase in the set time period for the heat-cleaning process.

This can be accomplished in accordance with the present invention by designing the timer switch itself as a blocking device for the locking element in such a way that the bimetal device causes a blocking of the timer switch against forward rotation when the temperature of the oven is within a defined range above a set value.

The advantages realized with the present invention are mainly that while the oven temperature is in this definedrange, it is possible to securely lock the oven door as well as simultaneously prevent turning of the timer forward to its wound position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional plan view of an oven timer provided with blocking elements in accordance with the present invention.

FIG. 2 is a front elevational view of a portion of the structure of FIG. 1, with plate 30 and knob 4 removed, with the blocking elements in their rest position.

FIG. 3 is a view similar to that of FIG. 2 with the blocking elements in the operating position.

FIG. 4 is a cross-sectional side view of an oven locking system including the timer of FIG. 1 in operating connection with a locking device for the door of an oven according to the present invention.

FIG. 5 is a schematic circuit diagram of the heater control circuit for the embodiment of FIGS. 1-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows in cross section a timer for controlling the self-cleaning operation of an oven. The timing mechanism together with the winding mechanism of the timer is disposed between two supporting plates 1 and 2 which are clamped together by means of screw bolts (not shown). An actuating shaft 3 which passes through the supporting plates 1 and 2 serves to wind the timer switch. Movement of a rotary knob 4 fastened on the actuating shaft 3 causes rotation of the shaft and thus winding of the timer. A toothed wheel 5 which is mounted on the actuating shaft 3 engages a driving gear 7 mounted on a shaft 6 which'is supported by the two 1 supporting plates 1 and 2. Toothed wheel 5 drives the driving gear 7 when the actuating shaft 3 is rotated. One end of shaft 6 is mounted in supporting plate 1 in an elongated bearing hole 6' and is biased towards the left side of the elongated bearing hole by means of a pressure spring 6" which is fastened to supporting plate 1. A toothed wheel 8 is mounted on shaft 6 to be rotatable relative thereto and is guided by friction disc springs 9,9. The association of the friction springs 9,9 with the toothed wheel 8 to produce a clutch-type friction coupling results in the advantage that the toothed wheel 8 can be rotated, independent of the driving gear 7, in a clockwise as well as a counterclockwise direction. The toothed wheel 8 guided by friction springs 9,9 is arranged in engagement with a pinion 10, mounted on a shaft 11 which is also mounted in supporting plates 1, 2. The structure described thus far is identical with that shown in FIG. l4 of US. Pat. No. 3,625,197.

On the end of shaft 11, which passes through the front supporting plate 2, a further pinion 12 is disposed. Pinion l2 cooperates with a device which will be described below for blocking the actuating shaft 3 in the forward time setting direction.

A conventional clock spring 14 is mounted on the end portion 13 of the actuating shaft 3 which passes.

through supporting plate 1, so that spring 14 is wound when the actuating shaft is rotated clockwise as shown by the arrow in FIG. 2. Abutment discs 15 and 15' provided with cams are also placed on the end portion 13 of the actuating shaft 3. These abutment discs act on switching contacts 16 of a switching device for controlling the heating circuit as shown in FIG. 5.

The pinion 12, which is partially accommodated within a guide sleeve 17 mounted in supporting plate 2 and cooperates with a small toothed wheel 18 disposed in front of the supporting plate 2. The toothed wheel 18 is connected to a driving pinion 19. The driving pinion 19 is mounted on a bearing shaft 20, the end of which is mounted in a two-armed rocker 22. The two-armed rocker 22 is additionally pivotally mounted on the guide sleeve 17 mounted in supporting plate 2. Thus sleeve 17 is the stationary fulcrum for pivotal movement of rocker 22.

As can be seen from FIGS. 2 and 3, an upwardly facing abutment surface 24 is disposed on one arm 23 of the two-armed rocker 22. A spring arm 26 of a twoarmed spring 27 acts from above in a downward direction on the other arm 25 of rocker 22 which is opposite the abutment surface 24. A bentover abutment flap 28 (FIG. 1) is provided for enabling the engagement of the spring arm 26 with the rocker 22.

The driving pinion 19 is in operative connection with an eccentric cam disc 29 having cam 29. A portion of the periphery of disc 29 is provided with teeth 42. The cam disc 29 is also fastened to actuating shaft 3. The eccentric cam disc 29 with the associated driving pinion 19 and toothed wheel 18, as well as the two-armed rocker 22 with the associated two-armed spring 27, form the device which cancels, or suppresses, the action of friction springs 9 and 9 and prevents advancement of the rotary knob 4 and thus unauthorized resetting of the winding mechanism of the timer. A safety plate 30 (FIG. 1) covers the front portion of the abovementioned parts of this device on the side facing the rotary knob 4. The safety plate 30 is connected to the supporting plate 2 while leaving a space 43 for installation of the above described blocking device.

The abutment surface 24 of rocker 22 is arranged to be operatively associated with a movable abutment pin 31. Pin 31 which is mounted in the free end of a deflecting bimetal strip 32, is designed to be adjustable in height to achieve proper operating alignment. The bimetal strip 32 is fastened to a block portion 33 having a large mass and made of a good heat conducting material. Strip 32 is connected therewith in a good heat conducting relationship. An electrical heating element 34 is associated with the block portion 33. Elements 32,33 and 34 form a bimetal control unit which constitutes a structural unit with the timer. As shown in FIG. 5, the heating element 34 is connected in series with the heating circuit of an oven heating mechanism 35, which circuit is controlled by the switching contacts 16 of the timer. This arrangement assures that the heating element 34 whose operation will be described below, can receive a heating voltage only when the oven heating mechanism 35 has also been switched on. The oven heating element 35 is switched on by the oven switch I 35' which is connected to the electrical power line.

FIG. 4 provides a partial side view of the front section of the oven including the timer, the actuating mechanism and the locking device. When the actuating shaft 3 is rotated for the purpose of winding the clock spring 14 a locking slide member 38 which is normally biased upwards by spring 53, is simultaneously actuated via an eccentric disc 37 fastened on actuating shaft 3. This locking slide 38 is moved downwardly by the disc 37 and engages slot 54 of the door 39 of a partially shown oven 40 and locks the door during the heat cleaning period, (i.e., while the timer, which controls the sequence of the heat-cleaning process, runs down,) thus preventing the door from being opened during this period.

The operation of the timer 52 will now be explained in detail below. As can be seen in FIG. 2, the driving pinion l9 rests on top of the cam 29 of the eccentric cam disc 29 when the rotary knob 4 is in the zero time, or starting, position. At this time, the two-armed rocker 22 which cooperates with the toothed wheel 18 of the driving pinion 19 via pinion 12 is in an approximately horizontal position. The bimetal strip 32 which is initially unheated is in an extended position, where its free end is in its lowermost position.

By rotating the rotary knob 4 in a clockwise direction shown by the arrow in FIG. 2, (to wind the clock spring 14) the rear end of shaft 6 which until now has been pressed toward the left in the elongated bearing hole 6 of supporting plate 1 by pressure spring 6", is now pivoted toward the right in the elongated bearing hole 6' by the rotation of toothed wheel 5 thus removing toothed wheel 8 from engagement with the associated pinion 10. As soon as the toothed wheel 8 is out of engagement with pinion 10, the clock spring 14 can be easily wound.

The eccentric cam disc 29, coupled with actuating shaft 3, rotates in the direction shown by the arrow in FIG. 2. Driving pinion 19 first moves without interference along the smooth running surface 41 following cam 29'. With continued rotation of the eccentric cam disc 29, the portion of the cam disc which has a slightly smaller diameter then lies opposites the driving pinion 19. The driving pinion 19, which is connected to the horizontally disposed rocker 22 and remains in its initial position, is spaced from the teeth 42 on the periphery of cam disc 29 and unable to engage therewith. The two-armed rocker 22, which is biased by the compression force from the two-armed spring 27, has the upward movement of its arm 23 limited by the abutment pin 31 of the extended bimetal strip 32.

The rotary knob 4 of the winding mechanism of the timer can now be turned in the forward winding or backward resetting direction without interference because of the action of friction springs 9, 9' since the backward movement of rotary knob 4 causes the toothed wheel 8 to slide between friction springs 9, 9' and consequently rotation of the knob is not blocked. As long as the heating circuit which is controlled by the timer, and also the associated heating element 34 which heats the blocking part 33 are not connected at all with the current source, the clock spring 14 can be wound up as often and as completely as desired and also can be reset to zero again at any time by rotating the rotary knob 4 back to its starting position.

Once, however, the heating circuit of a device, for example an electric oven with a device for automatically heat-cleaning the oven, is connected with the current source, rotation of the rotary knob 4 will close the switching contacts 16 disposed in the heating circuit of the oven heating mechanism 35 through the cams on the abutment discs 15, 15' as soon as a certain range of rotation has been traversed. Closing of the switching contacts 16 simultaneously applies voltage to the heating element 34 for heating the block portion 33. This heating element 34 is connected in series with the oven heating mechanism 35 and with the switching contacts 16 and consequently is controlled in dependence upon the heat being applied in the oven. The block portion 33 is only slowly heated however due to its large mass so that the bimetallic strip 32 fastened to the block portion 33 will bend upwardly only after a certain period of time, as shown in FIG. 3. The shift in the position of the bimetal strip causes the abutment pin 31 to be moved upwardly which relieves the restraint on arm 23. The two-armed rocker 22 which is under compression pressure from the two-armed spring 27 and in whose rocker arm 25 the toothed wheel 18 is mounted with the driving pinion 19, can now be pivoted in such a way that the position of the driving pinion 19 is shifted so that the pinion 19 engages the teeth 42 of cam disc 29. The pivoted driving pinion 19 is now coupled with the cam disc 29. The resulting efiect of this operation is the cancellation or bridging, of the force of the friction springs 9, 9' on the driving gear 7 which is disposed on shaft 6 and cooperates with toothed wheel 5 of the actuating shaft 3. After pivoting of driving pinion 19 and engagement with the teeth 42 of the cam disc 29, there consequently no longer exists a possibility for manually rotating the rotary knob 4 for moving the actuating shaft 3 back into its starting position or in a direction against the winding operation of the clock spring 14. The heat-cleaning process which is controlled by the timer therefore, can now take place without any outside interference.

When clock spring 14 has run down the abutment discs 15, 15' open the switching contacts 16 disposed in the circuit for the oven heating mechanism 35. The current circuit for the oven heating mechanism 35 as well as heating element 34 for heating blocking portion 33 is interrupted. Together with the running down of clock spring 14 the eccentric cam disc 29 simultaneously returns to its starting position which it has reached when clock spring 14 has completely run down and the driving pinion 19 again comes to rest on the cam 29'. At that point the rocker 22 which is coupled with bearing shaft is pivoted back into its horizontal position by cam 29'.

Due to the fact that the block portion 33 is designed as a heat storage block, it is advantageously accomplished that even when the current is interrupted the rotary knob 4 still can not be turned\back for a certain period of time since the bimetallic strip 32 is still being heated and consequently is bent upwardly Rocker 22, therefore, positively remains in the pivoted position and the driving pinion 19 remains in engagement with teeth 42 of the eccentric cam disc 29. If after a certain period of time, the blocking portion 33 has sufficiently cooled the bimetallic strip 32 returns to its horizontal starting position and thus allows the rocker to return to its horizontal position with its abutment pin 31, mounted in the bent-out end, acting downwardly on the abutment surface 24 of the rocker arm 23 of rocker 22.

Thus the driving pinion 19 is removed from engagement with teeth 42 of the eccentric cam disc. If now the rotary knob 4 is turned back, the eccentric disc 37 mounted on the actuating shaft 3 is simultaneously turned back in addition to the cam disc 29 so that the locking slide 38 returns to its original position and releases the blocking of the oven door 39. Now the oven 40, which in the meantime has cooled down to a temperature which harbors no danger for the user can be safely opened.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. For use in a kitchen oven equipped with apparatus for automatically heat-cleaning the interior surfaces of the oven, locking means for locking the oven door during the heat-cleaning process and having a locking member under spring tension and movable into a locking position, a locking control system comprising, in combination: timing means for controlling the operation of the heat-cleaning apparatus and arranged to be operatively connected with the locking member; blocking means connected to said timing means and arranged to be operatively connected with the locking member for holding the locking member in its locked position for a defined period of time; and bimetal control means connected for actuating said blocking means and for preventing said timing means from being reset while the temperature in the oven is above a defined value.

2. A device as defined in claim 11 further comprising an actuating shaft and means friction coupling said shaft to said timing means, and wherein said bimetal control means bridges said friction coupling means.

3. A device as defined in claim 1 wherein said bimetal control means includes an independent heating element and means for controlling said heating element in dependence upon the temperature of the oven.

4. A device as defined in claim 1 wherein said timing means and said bimetal control means fomi a structural Unit. 

1. For use in a kitchen oven equipped with apparatus for automatically heat-cleaning the interior surfaces of the oven, locking means for locking the oven door during the heat-cleaning process and having a locking member under spring tension and movable into a locking position, a locking control system comprising, in combination: timing means for controlling the operation of the heat-cleaning apparatus and arranged to be operatively connected with the locking member; blocking means connected to said timing means and arranged to be operatively connected with the locking member for holding the locking member in its locked position for a defined period of time; and bimetal control means connected for actuating said blocking means and for preventing said timing means from being reset while the temperature in the oven is above a defined value.
 2. A device as defined in claim 1 further comprising an actuating shaft and means friction coupling said shaft to said timing means, and wherein said bimetal control means bridges said friction coupling means.
 3. A device as defined in claim 1 wherein said bimetal control means includes an independent heating element and means for controlling said heating element in dependence upon the temperature of the oven.
 4. A device as defined in claim 1 wherein said timing means and said bimetal control means form a structural unit. 